This invention relates generally to a method and a system of sampling large regions of liquids for debris which easily attach to bubbles. More specifically, it relates to a method of generating large regions of bubbles in pools by means of dispersing chemically coated particles for the purpose of bringing debris to the surface, frequently associated with efforts to cleanse such regions, pools, or lakes.
Bubbles are important to many processes related to chemical engineering. Chemical engineers introduce bubbles into liquids to increase gas-liquid contacting, to agitate the liquid phase, and to produce foams and froths. Bubbles are also used to clean "dirty" liquids. A conventional bubbler (such as a device with many small holes through which a gas is passed) is placed near the bottom of a tank containing the dirty liquid. As bubbles rise to the surface they collect "debris", and carry it to the surface. A vacuum system can then be used to remove the debris from the surface.
Debris means any substance which is collected by the bubbles. It includes, but is not limited to, surfactant molecules, macro-molecules (like proteins and DNA fragments), oils (natural and synthetic), particulates (like dead organisms, soot, or mud), bacteria, pollutants, and micro-organisms (like algae). Pools mean any large body of water, including ponds, lakes, swimming pools, vats, tanks, bays, reservoirs, and oceans.
The bubbles generated in conjunction with the present method are formed from very large numbers (as large as billions or trillions) of dispersed chemically coated particles (typically less than 1 cm, and as small as 1 micron diameter) which will generate the desired bubbles.
Heretofore, chemical engineers have introduced bubbles into liquids either by violent mixing or by blowing gas through a perforated device having small holes submerged in the liquid. Both methods require immediate access to power and mechanical equipment. A new method is disclosed herein which represents a new technology not previously known or used for this purpose.
Virtually all bubble related phenomena are dependent upon the number and size distribution of bubbles present. The method described herein relates to the production of vast bubble-containing regions or patches where the shape of the region, and the size and number of bubbles, is controlled.
Water is frequently being sampled to determine the amount of pollutants, or biological organisms, or the turbidity, etc. Frequently, a number of small samples (on the order of a gallon) are extracted and analyzed to make predictions about average pollutant levels within the pool. A difficulty with this method is that the quantity being measured (say number of organisms per cm.sup.3) can vary dramatically throughout the pool, and from a practical standpoint only a limited number of samples can be taken.
Previous methods have been employed to produce bubbles by releasing solid reactant into a liquid. They have suffered two drawbacks. They had little control over the bubble spectra (that is, the number of bubbles as a function of bubble diameter); and only a limited region could be exposed to the reactant. The present method overcomes these two drawbacks, and requires no special mechanical equipment or energy sources apart from that related to dispersing the particles.
The method is based on the well known ability of bubbles to scavenge particles that they pass when rising through the water. A laboratory method for cleaning water is to bubble it for several hours.